Ink jet printers are well known in the prior art and one characteristic example is shown in U.S. Pat. No. 3,769,624 granted on Oct. 30, 1973, to Lee et al. In such ink jet printers drops of ink are formed from a stream of ink flowing from a nozzle. The normal flow path of the ink impinges on a mask. However, any ink drops that are to be printed on the paper are charged and deflected out of the original or normal path into a second path which impinges upon an appropriate place on the paper. Uncharged ink continues on the original or normal path which is substantially the axis of the nozzle and strikes the mask or catcher and proceeds from the mask to a waste container or is recycled through the nozzle.
Problems have arisen with common catchers or masks in that many masks are substantially a planar surface at right angles to the path of ink. This results in a high impact of the drops of ink on the mask, causing the drops to spatter or produce a mist which can interfere with the operation of the printer and contaminate the entire machine. Additionally, the drops of ink that strike the mask must be readily conducted away.
The knife edge of the mask is the decision line between those drops caught by the mask and those drops which are sufficiently deflected so as successfully to avoid the mask and strike the paper. A partially deflected drop that strikes the knife edge head-on, as will occasionally happen in an ink jet printer, can leave a build-up or a blob of ink on top of the knife edge. A blob on the knife edge will raise the effective height and thickness of the knife edge in the region of the blob and thus being to stop drops that should not be stopped.
It is an object of the present invention to assure that drops of ink stopped by an ink jet mask do not remain and buildup on the knife edge of the mask.
It is also an object of the present invention to prevent or minimize spattering of ink that strikes the mask of an ink jet printer.
It is still another object of the present invention to conduct waste ink away from the knife edge of an ink jet mask in an ink jet printer simply, reliably and inexpensively.
Yet another object of the present invention is keep an ink-jet printer mask clean.